The organic chemical hydride process for hydrogenating aromatic compounds such as toluene has recently been developed for the purposes of storing and transporting hydrogen in the form of organic hydrides (hydrogenated aromatic compound). According to this process, hydrogen is converted into an organic hydride at the site of production of hydrogen, and transported in the form of the organic hydride. The organic hydride is separated into the hydrogen and the aromatic compound at a plant or a hydrogen station located near a city or other user of hydrogen by dehydrogenating the organic hydride. The aromatic compound produced from this dehydrogenation process is transported back to the production site of hydrogen to be hydrogenated by hydrogen once again.
It is known that the catalyst used for the dehydrogenation process is degraded over time by carbon originating from a poisoning substance (such as biphenyl produced at the time of hydrogenating the aromatic compound) which is deposited on the surface of the dehydrogenation catalyst (by carbonation), and this may significantly limit the activity (or the service life) of the catalyst.
It is also known to control the reduction in catalyst activity by preventing the deposition of carbon on the dehydrogenation catalyst by circulating a part of the hydrogen that is produced in the dehydrogenation reaction unit by the dehydrogenation reaction of an organic hydride (or by circulating externally supplied hydrogen in the catalyst layer) (See Patent Documents 1 and 2). Such prior art does not require an external source of hydrogen, and eliminates the need for adjusting the purity of the hydrogen when the hydrogen is supplied from an external source.